How do I write a prescription for insulin lispro (Humalog) 100 units/mL for continuous subcutaneous infusion via insulin pump in a patient with type 1 diabetes (or insulin‑requiring type 2) trained in pump therapy?

How to Write a Prescription for Insulin Lispro 100 units/mL for Insulin Pump Therapy

Prescribe insulin lispro (Humalog) 100 units/mL vial or cartridge for continuous subcutaneous insulin infusion (CSII), specifying the quantity based on the patient's total daily insulin dose with adequate supply for 1-3 months, and include backup rapid-acting insulin syringes or pens for pump failure emergencies. 1, 2

Essential Prescription Components

Medication Specification

• Drug name and concentration: Insulin lispro 100 units/mL (Humalog 100 units/mL) 3
• Formulation: Vial or pump cartridge (depending on pump compatibility) 1
• Route: For continuous subcutaneous insulin infusion via insulin pump 3

Quantity Calculation

• Calculate based on total daily insulin dose (typically 0.4-1.0 units/kg/day, with 0.5 units/kg/day as a typical starting dose for metabolically stable patients) 3
• Most pump reservoirs hold 200-300 units, providing 4-6 days of insulin for patients using 50 units daily 1
• Dispense quantity: Provide enough for 30-90 days (e.g., if patient uses 50 units/day, dispense 2-3 vials of 1000 units each for a 1-month supply) 1

Critical Safety Requirements

• Mandatory backup supply: Always prescribe backup rapid-acting insulin syringes or pens separately, as pump failure can lead to ketoacidosis within hours since no long-acting insulin is on board 1, 2
• Include glucagon prescription for all patients on insulin pump therapy 3

Why Lispro is the Preferred Pump Insulin

Rapid-acting insulin analogs like lispro are the standard of care for insulin pumps because they provide superior postprandial glucose control compared to regular human insulin when delivered by CSII. 3, 2 The American Diabetes Association confirms that lispro's stability in pump systems has been validated, and controlled trials demonstrate improved postprandial glucose control versus regular insulin. 3, 2

Pharmacokinetic Advantages

• Peak serum insulin concentration is three times higher than regular insulin 4
• Time to peak is 4.2 times faster 4
• Absorption rate constant is double that of regular insulin 4
• Duration of action is half as long, reducing delayed hypoglycemia risk 4, 5

Sample Prescription Format

Rx: Insulin lispro (Humalog) 100 units/mL

• Quantity: [Calculate based on patient's TDD × 30-90 days] vials or cartridges
• Indication: For continuous subcutaneous insulin infusion via insulin pump
• Instructions: Load into insulin pump reservoir per pump manufacturer instructions. Change infusion set every 2-3 days.
• Refills: [Appropriate number for coverage period]

Rx: Insulin lispro (Humalog) 100 units/mL pen or vial (backup supply)

• Quantity: 1-2 pens or 1 vial
• Instructions: For emergency use if pump fails. Administer subcutaneously as directed by diabetes care team.

Critical Pitfalls to Avoid

Never Use Long-Acting Insulins in Pumps

• Do not prescribe glargine, detemir, or degludec for pump use — these are designed for once or twice daily injection, not continuous infusion 1, 2
• The pump itself provides basal coverage through continuous delivery of rapid-acting insulin 2

Do Not Mix Insulins in Pump Reservoirs

• Use of insulin mixtures in pumps has not been evaluated and is not recommended 3
• Only use pure rapid-acting analog formulations 3

Patient Selection Requirements

• Verify patient is strongly motivated, trained in pump therapy, demonstrates competent self-monitoring of blood glucose, and understands pump operation 3
• Ensure patient has access to skilled professional team familiar with CSII therapy 3

Pregnancy Consideration

• Note that rapid-acting insulin analogs are not FDA-approved for use in pregnancy, though this applies to the analog formulation itself rather than pump use specifically 3

Pump Insulin Delivery Pattern

• Approximately 50% of total daily insulin is delivered as continuous basal infusion throughout 24 hours 1, 2
• Remaining 50% is delivered as meal boluses 1, 2
• This requires insulin that can be safely administered in small, frequent doses continuously 2